The spin is the catch – studying fission with traps

Project title: The spin is the catch – studying fission with traps
Main applicant: Stephan Pomp, Division of Applied Nuclear Physics
Grant amount: 2 920 000 SEK for the period 2021-2024

We use the latest experimental advances in nuclear mass measurement techniques to study phenomena in nuclear dynamics on the attosecond timescale, in particular the open question for mechanisms that generate the remarkably large angular momenta observed for fission fragments. We tackle this question is my measuring isomeric yield ratios (IYR) by direct ion counting which is superior to the generally used gamma spectroscopic methods. The relative population of the different spin states is then used to extrapolate back to the angular momentum of the fission fragment right after scission has occurred.

Three measurements will be performed; one at IGISOL/JYFLTRAP in Jyväskylä, Finland, one at TRIGATRAP in Mainz, Germany, and another at CSC/MR-TOF at GSI, Germany. In the former two campaigns, IYR resulting from fission of 234U* produced in two different ways will be measured. The latter measures IYR for spontaneous fission of 252Cf. All these campaigns are feasible and can be conduced already during autumn 2020 or in 2021.

We build upon our first measurements of IYR with the direct ion counting technique and use recent advances in mass resolving power of Penning traps and multi-reflection time-of-flight systems, achieving mass resolving powers in excess of 106.

Systematic studies of IYR in the 132Sn region and the region of complementary fission fragments will be measured and the angular momenta of the nascent fission fragments will be deduced and compared to model calculations.